1. Field of the Invention
The present process is directed to the production of dinitriles and more particularly, to the production of adiponitrile by the hydrocyanation of 3- and/or 4-pentenenitriles in the presence of a zero-valent nickel catalyst promoted by an organoborane wherein the catalyst efficiency is maximized; the amount of promoter required to sustain a satisfactory reaction is minimized and operation at desirably low temperatures is more readily achieved.
2. Description of the Prior Art
U.S. Pat. No. 3,496,218 issued on Feb. 17, 1970 describes in general terms a process for the preparation of dinitriles especially adiponitrile by the hydrocyanation of non-conjugated, ethylenically unsaturated organic compounds, e.g., 3- and/or 4-pentenenitriles using certain nickel complexes as catalysts. The catalysts are promoted by organoborane compounds such as triphenylborane. A wide range of process conditions and relative amounts and types of reactants are disclosed. In addition, the patentee discloses that at least a two mol excess ligand with respect to the nickel complex can be employed but that there is little advantage in exceeding a 300 molar excess. The use of excess ligand which can be the same or different than the ligand attached to the nickel in the nickel complex is taught to improve product distribution and to extend catalyst life. The minimum amount of ligand exemplified by the patentee using the promoter herein disclosed is approximately 14 mols of total ligand for each mol of zero-valent nickel (14/1) with the majority of examples disclosing about 24/1.
A particularly useful form of zero-valent nickel catalyst is described in U.S. Pat. No. 3,766,237 issued on Oct. 16, 1973. The patentees disclose the use of an excess of the triarylphosphite ligand in the hydrocyanation along with the addition of certain ethers to improve the yield and increase the pounds of product which can be made per pound of catalyst consumed. The patentees teach that at least six and preferably at least 12 mols of total ligand per mol of zero-valent nickel can be employed and exemplify a minimum of 13 using the herein-described promoter.
For a different reaction the use of at least a one and preferably at least a two molar excess of a variety of ligands in a catalyst employed for the isomerization of 2-methyl-3-butenenitrile is disclosed in U.S. Pat. No. 3,853,948 issued on Dec. 10, 1974.